The discovery was led by University of Otago (Christchurch) pathology and biomedical science associate professor Logan Walker, who said the development of a risk-reducing drug project had already received funding and would be led by the university.
The initial study was the world’s largest of women known to have mutations of the breast cancer genes — BRCA1 and BRCA2.
It made two significant discoveries, he said.
"We have found a gene — the SULT1A1 — that may help doctors decrease the chance of women getting breast cancer, especially if they have also inherited a mutation in the BRCA1 gene.
"We have also found that women who have inherited a BRCA1 gene with segments missing are, for reasons as yet unknown, at the highest risk of developing breast cancer."
The study, in collaboration with the international Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA), involved about 26,000 women known to have mutations in the BRCA1 or BRCA2 genes, and 166 researchers from 160 institutes worldwide.
In New Zealand, about one in every 250 individuals inherit a genetic mutation in these two genes, which means they are at high risk of developing breast and ovarian cancer.
Prof Walker said at present, the most effective risk-reducing strategy for these women at high risk of breast cancer was a bilateral mastectomy.
Although effective, the approach was irreversible and could cause ongoing psychological and physiological harm to patients, especially for younger women.
He said the study found that reduced levels of the protein produced by the SULT1A1 gene played an important role in the metabolism of cancer-causing agents and lowered the risk of breast cancer.
"When we turned down the activity of the SULT1A1 gene in breast cells, the cells grew more slowly and were more resistant to DNA damage.
"This anti-cancer-like feature supported epidemiological results from 26,000 women," he said.
The next step was to develop a risk-reducing drug — a project which will be led by Otago’s Dr George Wiggins.
He said prophylactic drug treatments were becoming well established for the prevention of different diseases.
"For example, aspirin, statins and anti-hypertensive therapies have had a major impact on reducing incidence of cardiovascular disease and extending life expectancy.
"By comparison, progress in therapeutic intervention to prevent breast cancer has been poor.
"Providing a non-invasive and easily accessible preventative therapy for women at high risk of developing breast cancer would have numerous benefits for the health system, and for the patients and their whanau.
"Such a therapy could give genetically predisposed young women the opportunity to bear and breastfeed their children by delaying or supplanting the need for risk-reducing surgery."
Prof Walker said effective prevention strategies for women at increased risk of breast cancer were also vital for controlling and reducing the social and economic impact of the disease.
